A correlation was found between the times at which the Sun crosses the spiral arms and six known mass extinction events. Furthermore, we identify five additional historical mass extinction events that might be explained by the motion of the Sun around our Galaxy. These five additional significant drops in marine genera that we find include significant reductions in diversity at 415, 322, 300, 145 and 33 Myr ago. Our simulations indicate that the Sun has spent ~60% of its time passing through our Galaxy’s various spiral arms.

The figure on the right, from their paper, shows the Sun’s orbit in red over the last half billion years. The Sun’s present position is indicated by the yellow spot, and the eleven extinctions are indicated by the circles.

There are obviously a great deal of uncertainties in this conclusion. Most significantly, the shape and history of the Milky Way remains very much in doubt, especially since we reside within it and cannot really get a good look at it. Though in recent years astronomers have assembled a reasonable image of the galaxy’s shape — a barred spiral with two major arms and several minor ones — this picture includes many assumptions that could very easily be wrong.

Back from the dead! A new study has found that scientists are significantly over-estimating the number of animal extinctions, with approximately one third of the so-called “extinct” species turning up alive. This quote makes one wonder if politics have been a factor:

The mistakes cannot be blamed on primitive technology or old fashioned scientific methods. “Mammals missing in the 20th century were nearly three times as likely to be rediscovered as those that disappeared in the 19th century.”

“Not simply about one mission, [Genesis] is also the history of America’s quest for the moon… Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America’s greatest human triumphs.” –San Antonio Express-News